8.1. Visualize:Solve:Figure (i) shows a weightlifter (WL) holding a heavy barbell (BB) across his shoulders. He is standing ona rough surface (S) that is a part of the earth (E). We distinguish between the surface (S), which exerts a contactforce, and the earth, which exerts the long range force of gravity. Figure (ii) shows the barbell, the weightlifter, andthe earth separated from one another. This separation helps to indicate the forces acting on each object. Figures (iii)and (iv) are free body diagrams for the barbell and the weightlifter, respectively.Altogether there are four interactions. There is the interaction between the barbell and the weightlifter, theweightlifter and the surface of the earth (contact force), the barbell and the earth, and the weightlifter and the earth.The interaction between the barbell and the weightlifter leads to two forces: rFWL on BBand rFBB on WL. These are anaction/reaction pair. The interaction between the weightlifter and the surface of the earth is a contact interactionleading to rnS on WLand rnWL on S. These two forces also constitute an action/reaction pair. The weight force rwE on BBhas its action/reaction force rwBB on E, and the weight force rwE on WLhas its action/reaction force rwWL on E.

This
preview
has intentionally blurred sections.
Sign up to view the full version.

8.2. Visualize:Solve:Figure (i) shows a softball player (P) with a ball (B) in her hand that has come forward beside her headand is just about ready to release the ball. We have represented the earth (E) and its rough surface (S). Contactforces exist between the surface and the softball player. Figure (ii) shows the ball, the player, and the earthseparated. This separation helps to indicate the various forces on each object. We have altogether 6 interactions.The action/reaction pairs of all the forces have been indicated by dotted lines. Figure (iii) shows the free-bodydiagrams for the ball and the softball player.

8.3. Visualize:Solve:Figure (i) shows the head-on collision of a bowling ball (BB) and a soccer ball (SB) on a hard surface (S)of the earth (E). There are 3 types of interactions in the present case: between the bowling ball and the soccer ball,between the earth and the balls (long-range force of gravity), and between the balls and the surface (contact force).Figure (ii) shows the bowling ball, the soccer ball, and the surface separated from one another. The force on thebowling ball due to the soccer ball rFSB on BBand the force on the soccer ball due to the bowling ball rFBB on SBmakean action/reaction pair. The weights rwE on SBand rwSB on Eare an action/reaction pair, and so are the weights rwE on BBand rwBB on E. The contact forces rnS on BBand rnS on SBhave action/reaction forces in rnBB on Sand rnSB on S, respectively.All the action/reaction pairs are indicated by dotted lines. Figure (iii) shows the free-body diagrams for the bowlingball and the soccer ball.

This
preview
has intentionally blurred sections.
Sign up to view the full version.

8.4. Visualize:Solve:Figure (i) shows the mountain climber (C), the rope (R), the bag of supplies (B), the surface of themountain (S), and the earth (E). To indicate the forces on each of the various objects, we have separated C, R, B, S,

This is the end of the preview.
Sign up
to
access the rest of the document.